(Adapted from the applicant's abstract) This proposal is for the establishment of a Specialized Center of Research in Hematopoietic Stem Cell (HSC) Biology at the Childrens Hospital Los Angeles (CHLA). The programmatic focus of the grant is the isolation and genetic modification of HSC for the purpose of improving the treatment of patients with hematological, genetic and immunological diseases. The grant is multi-disciplinary in nature with investigators from CHLA, the UCLA School of Medicine and the USC School of Medicine and contains research in the areas of HSC isolation, HSC differentiation, clinical bone marrow transplantation (BMT), hematopoietic and lymphoid growth factors, immunology, gene transduction and clinical gene therapy. The proposal contains four Projects and four Cores, including an Administrative Core that contains two pilot projects by junior investigators. The Scientific Aims include 1) the role of homeobox genes in the regulation of HSC differentiation; 2) the evaluation of HSC gene transduction in an in vivo xenogeneic bnx/hu mouse model; 3) the determination of the role of growth factors [IL-7, stem cell factor (SCF)] in T lymphopoiesis; 4) the determination of the in vivo repopulating capacity of high purified human HSC (CD34+, CD38-cells); and 5) clinical gene therapy trials for adenosine deaminase (ADA) deficiency and Gaucher disease. The SCOR will support a monthly seminar series and a bi- annual Gene Therapy Symposium. Overall the application is an attempt to integrate basic research, pre-clinical investigation and clinical protocols with the ultimate goal of improving therapy for patients with hematological, genetic and immunological diseases.